Liquid crystal display device with shield casing connected to frame holding the display above lower casing holding light source

ABSTRACT

A liquid crystal display device which includes a shield casing made of a metal plate and having fixing pawls and fixing hooks, an middle frame for holding a liquid crystal display, and a lower casing for packaging back lights. The fixing pawls of said shield casing are bent in corresponding recesses formed in the middle frame. Also, the fixing hooks of said shield casing are fitted on corresponding projections formed on the lower casing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device and,more particularly, to a liquid crystal display device of active matrixtype using thin film transistors or the like.

2. Prior Art

In a liquid crystal display device of active matrix type, non-lineardevices (e.g., switching devices) are disposed in a manner to correspondto a plurality of pixel electrodes arranged in matrix, respectively. Theliquid crystal in each pixel is always drive, in principle, (at a dutyratio of 1.0). In comparison with the so-called "simple matrix type"which employs a time division driving system, therefore, the activesystem has better contrast and has become an indispensable techniqueparticularly in a color liquid crystal display device. A typical exampleof the switching devices is a thin film transistor (TFT).

A liquid crystal display circuit (or a liquid crystal display panel) isconstructed: by superposing a lower substrate, which is formed, over alower transparent glass substrate with reference to a liquid crystallayer, sequentially with a thin film transistor, a transparent pixelelectrode, a passivation film for the thin film transistor, and a lowerorientation film for orienting liquid crystal molecules; and an uppersubstrate, which is formed over an upper transparent glass substratesequentially with a black matrix, a color filter, a passivation film forthe color filter, a common transparent pixel electrode and an upperorientation film, such that their orientation films are opposed to eachother; by bonding the two substrates by a sealing material arrangedaround the edges of the substrates; and by sealing up the liquidcrystals between the two substrates. Incidentally, a back light isarranged at the side of the lower substrate.

Here, the liquid crystal display device of active matrix type using thethin film transistors is known in Japanese Patent Laid-Open No.309921/1988 or on pp. 193 to 210 of Nikkei Electronics entitled "ActiveMatrix Type Color Liquid Crystal Display of 12.5 Type Adopting RedundantConstruction" and issued on Dec. 15, 1986 by NIKKEI McGRAW-HILL, forexample.

SUMMARY OF THE INVENTION

Since a shield casing made of a metal plate or a liquid crystal displaycircuit is fixed by means of rivets, the liquid crystal display deviceof the prior art is troubled by a difficulty in repair or replacement ofthe back lights.

An object of the present invention is to provide a liquid crystaldisplay device which can be easily repaired or repaired in its backlights.

According to one embodiment of the present invention, there is provideda liquid crystal display device which comprises: a shield casing made ofa metal plate and having fixing pawls and fixing hooks; an middle framefor holding a liquid crystal display; and a lower casing for packagingback lights, wherein the fixing pawls of said shield casing are bent incorresponding recesses formed in the middle frame, and wherein thefixing hooks of said shield casing are fitted on correspondingprojections formed on the lower casing.

The liquid crystal display device can be easily repaired and replaced inits back lights because the fixing pawls and hooks of the shield casingcan be easily removed and because the shield casing, the middle framefor holding the liquid crystal display and the lower casing forpackaging the back lights are easily assembled and disassembled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view showing an essential portion of one pixel ofthe liquid crystal display of a color liquid crystal display circuit ofactive matrix type, to which is applied the present invention;

FIG. 2 is a section taken along line 2--2 of FIG. 1 and shows one pixeland its peripheral portion;

FIG. 3 is a section taken along line 3--3 of FIG. 1 and shows anadditional capacitor Cadd;

FIG. 4 is a top plan view showing an essential portion of a liquidcrystal display circuit arranged with a plurality of pixels shown inFIG. 1;

FIG. 5 is a top plan view drawing only layers g2 and AS of the pixelshown in FIG. 1;

FIG. 6 is a top plan view drawing only layers d1, d2 and d3 of the pixelshown in FIG. 1;

FIG. 7 is a top plan view drawing only a pixel electrode layer, alight-shielding film and a color filter layer of the pixel shown in FIG.1;

FIG. 8 is a top plan view showing an essential portion of only the pixelelectrode layer, the light-shielding layer and the color filter layershown in FIG. 6;

FIGS. 9(A) and 9(B) present a top plan view and a section showing thevicinity of a connecting portion between a gate terminal GTM and a gatesignal line GL;

FIGS. 10(A) and 10(B) present a top plan view and a section showing thevicinity of a connecting portion between a drain terminal DTM and avideo signal line DL;

FIG. 11 is an equivalent circuit diagram showing a liquid crystaldisplay circuit of a color liquid crystal display device of activematrix type;

FIG. 12 is an equivalent circuit diagram showing the pixel shown in FIG.1;

FIG. 13 presents a flow chart of sections of a pixel portion and a gateterminal portion and shows the fabrication steps A to C at the side of asubstrate SUB1;

FIG. 14 presents a flow chart of sections of the pixel portion and thegate terminal portion and shows the fabrication steps D to F at the sideof the substrate SUB1;

FIG. 15 presents a flow chart of sections of the pixel portion and thegate terminal portion and shows the fabrication steps G to I at the sideof the substrate SUB1;

FIG. 16 is a top plan view for explaining the construction a matrixperipheral portion of a display panel;

FIG. 17 is a panel top plan view for exaggerating and explaining theperipheral portion of FIG. 16 more specifically;

FIG. 18 is an enlarged top plan view showing a corner of a display panelincluding an electric connection portion of upper and lower substrates;

FIG. 19 is a section showing the pixel portion of a matrix at the centerand the vicinity of a panel corner and the vicinity of a video signalterminal portion at the two sides;

FIG. 20 is a section showing panel edge portions with and without ascanning signal terminal at the lefthand and righthand sides;

FIG. 21 is a section showing a structure of a tape carrier package TCP,in which an integrated circuit chip CHI constituting a drive circuit ismounted on a flexible wiring substrate;

FIG. 22 is a section showing the state of an essential portion, in whichthe tape carrier package TCP is connected with a video signal circuitterminal DTP of a liquid crystal display panel PNL;

FIG. 23 is an exploded perspective view showing a liquid crystal displaymodule;

FIG. 24 presents upper side, front side, rear side, righthand side andlefthand side views of a shield casing of the liquid crystal displaymodule;

FIG. 25 is a perspective view showing the shield casing and taken fromthe upper side;

FIG. 26 is a upper side view showing the state, in which peripheraldrive circuits are packaged in the liquid crystal display panel;

FIG. 27 presents upper side, front side, rear side, righthand side andlefthand side views of a middle frame;

FIG. 28 is a lower side view showing the middle frame;

FIG. 29 is a perspective view showing the middle frame and taken fromthe upper side;

FIG. 30 is a lower side view showing a drive circuit substrate to bemounted on the middle frame;

FIG. 31 is an upper side view showing the connection state between theperipheral drive circuit substrate (as viewed from the upper side) ofthe liquid crystal display and the drive circuit substrate (as viewedfrom the lower side) to be mounted on the middle frame;

FIG. 32 presents upper side, rear side, righthand side and lefthand sideviews of a back light support;

FIG. 33 is a perspective view showing the back light support and takenfrom the upper side;

FIG. 34 presents upper side (or reflection side), rear side, righthandside and lefthand side of a lower casing;

FIG. 35 is a lower side view of the lower casing;

FIG. 36 is a perspective view showing the lower casing and taken fromthe upper side;

FIG. 37 presents upper side, rear side, righthand side and lefthand sideviews showing the state, in which the back light support, back lightsand an inverter circuit substrate are mounted in the lower casing;

FIG. 38 is a section (as taken along line 38--38 of FIG. 34) of thelower casing; and

FIG. 39 is a section taken along line 39--39 of FIG. 37.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention, other objects of the present invention, and otherfeatures of the present invention will become apparent from thefollowing description to be made with reference to the accompanyingdrawings.

ACTIVE MATRIX LIQUID CRYSTAL DISPLAY DEVICE

Here will be described in the following the construction of the presentinvention in connection with embodiments of a color liquid crystaldisplay device of active matrix type, to which is applied the presentinvention. Incidentally, the parts having identical functions aredesignated at identical reference characters throughout all the Figuresfor describing the embodiments, and their repeated descriptions will beomitted.

SUMMARY OF MATRIX PORTION

FIG. 1 is a top plan view showing one embodiment of one pixel and itsperipheral portion of the active matrix type color liquid crystaldisplay device to which is applied the present invention. FIG. 2 is asection taken along line 2--2 of FIG. 1. FIG. 3 is a section taken alongline 3--3 of FIG. 1. On the other hand, FIG. 4 is a top plan viewshowing the case in which a plurality of pixels shown in FIG. 1 arearranged.

As shown in FIG. 1, each pixel is arranged in a cross region (defined byfour signal lines) between two adjacent scanning signal lines (e.g.,gate signal lines or horizontal signal lines) GL and two video signallines (e.g., drain signal lines or vertical signal lines) DL. Each pixelincludes a thin film transistor TFT, a transparent pixel electrode ITO1and a latching capacitor Cadd. The scanning signal lines GL are extendedin the column direction and arranged in plurality in the row direction.The video signal lines DL are extended in the row direction and arrangedin plurality in the column direction.

As shown in FIG. 2, the thin film transistor TFT and the transparentpixel electrode ITO1 are formed at the side of a lower transparent glasssubstrate SUB1 across a liquid crystal layer LC, and a color film FILand a back matrix pattern BM for light shielding are formed at the sideof an upper transparent glass substrate SUB2. The side of the lowertransparent glass substrate SUB1 is made to have a thickness of about1.1 mm, for example. On the both surfaces of the transparent glasssubstrates SUB1 and SUB2, there are formed silicon oxide layers SIOwhich are deposited by the dip treatment. Accordingly, even if thereexist sharp defects at the surfaces of the transparent glass substratesSUB1 and SUB2, the scanning signal lines GL as well as the color filterFIL to be deposited thereon can be protected from the sharp defectssince the defects are covered with the silicon oxide layer SIO.

On the surface of the upper transparent glass substrate SUB2 at theinner side (or the side of the liquid crystal LC), there aresequentially laminated the light-shielding film BM, the color filterFIL, a passivation film PSV2, a common transparent pixel electrode ITO2(or COM) and an upper orientation film ORI2.

SUMMARY OF MATRIX PERIPHERY

FIG. 16 is a top plan view showing an essential portion of the peripheryof a matrix (AR) of a display panel PNL including the upper and lowerglass substrates SUB1 and SUB2. FIG. 17 is a top plan view furtherexaggerating the peripheral portion. FIG. 18 is an enlarged top planview showing the vicinity of a seal portion SL corresponding to thelefthand upper corner of the panel of FIGS. 16 and 17. Moreover, FIG. 19presents a section of FIG. 2 at the lefthand side, a section taken fromline 19a 19a of FIG. 18 at the righthand side, and a section showing thevicinity of an external connection terminal DTM, to which is connected avideo signal drive circuit. Likewise, FIG. 20 presents a section showingthe vicinity of an external connection terminal GTM, to which isconnected a scanning circuit, at the lefthand side and a section showingthe vicinity of a seal portion having no external connection terminal atthe righthand side.

In a fabrication of this panel, a plurality of devices aresimultaneously worked and divided by a single sheet of glass substrateso as to improve the throughput, if the panel has a small size, but aglass substrate having a standardized size for any kind is worked and isreduced to the sizes matching the individual kinds so as to share thefabrication facilities, if the size is large. In either case, the glassis cut after a series of steps. In FIGS. 16 to 18 showing the latterexample, FIGS. 16 and 17 show the state after the upper and lowersubstrates SUB1 and SUB2 have been cut, and FIG. 18 shows the statebefore the cutting operation. Letters LN designate the edges of the twosubstrates before the cutting operation, and characters CT1 and CT2designates the individual positions at which the substrates SUB1 andSUB2 are to be cut. In either case, the size of the upper substrate SUB2is so limited to the inside of the lower substrate SUB1 that theportions (as located at the upper and lower sides and the lefthand sidein the Figures), in which external connection terminal groups Tg and Td(although suffixes are omitted) are present in the completed state, maybe exposed to the outside. The terminal groups Tg and Td are named suchthat the scanning line connecting terminal GTM, the video signal circuitconnecting terminal DTM and their leading lines are collected inplurality at the unit of a tape carrier package TCP (as shown in FIGS.20 and 21) on which is packaged an integrated circuit chip CHI. Theleading line from the matrix portion of each group to the externalconnection terminal portion is inclined toward the two ends. This isbecause the terminals DTM and GTM of the display panel PNL are made tomatch the array pitch of the package TCP and the connection terminalpitch at each package TCP.

Between and along he edges of the transparent glass plates SUB1 andSUB2, there is formed the seal pattern SL for sealing the liquid crystalLC excepting a liquid crystal entrance INJ. The seal material is made ofan epoxy resin, for example. The common transparent pixel electrode ITO2at the side of the upper transparent glass substrate SUB2 is connectedat the four corners in the present embodiment with a leading line INT,which is formed at the side of the lower transparent glass substrateSUB1, in at least one portion by a silver paste material AGP. Theleading line INT is formed at the same fabrication step as that of thelater-described gate terminal GTM and drain terminal DTM.

The orientation films ORI1 and ORI2, the transparent pixel electrodeITO1, the common transparent pixel electrode ITO2, and the individuallayers are formed in the seal pattern SL. Polarization plates POL1 andPOL2 are individually formed on the outer surfaces of the lowertransparent glass substrate SUB1 and the upper transparent glasssubstrate SUB2. The liquid crystal LC is filled in the region which isdefined by the seal pattern SL between the lower orientation film ORI1and the upper orientation film ORI2 for setting the orientations of theliquid crystal molecules. The lower orientation film ORI1 is formed overa passivation film PSV1 at the side of the lower transparent glasssubstrate SUB1.

This liquid crystal display device is assembled: by superposing theindividual layers at the sides of the lower transparent glass substrateSUB1 and the upper transparent glass substrate SUB2; by forming the sealpattern SL at the side of the substrate SUB2; by superposing the lowertransparent glass substrate SUB1 and the upper transparent glasssubstrate SUB2; by injecting the liquid crystal LC from the opening INJof the seal member SL to seal the injection entrance INJ with the epoxyresin or the like; and by cutting the upper and lower substrates.

THIN FILM TRANSISTOR TFT

If a positive bias is applied to the gate electrode GT, the thin filmtransistor TFT has its channel resistance reduced between its source anddrain. If the bias is reduced to zero, the thin film transistor TFToperates to have its channel resistance increased.

The thin film transistor TFT of each pixel is divided into two (orplurality) in the pixel so that it is composed of thin film transistors(or divided thin film transistors) TFT1 and TFT2. These thin filmtransistors TFT1 and TFT2 are individually made to have a substantiallyequal size (in the channel length and width). Each of these divided thinfilm transistors TFT1 and TFT2 is composed mainly of a gate electrodeGT, a gate insulating film GI, an i-type (i.e., intrinsic type not dopedwith a conductivity type determining impurity) amorphous silicon (Si)semiconductor layer AS, and a pair of source electrode SD1 and drainelectrode SD2. Incidentally, the source and drain are intrinsicallydetermined in dependence upon the bias polarity inbetween, and thispolarity is inverted during the operation in the circuit of the presentdisplay device. Thus, it should be understood that the source and drainare interchanged during the operation. In the following description,however, one is fixed as the source whereas the other is fixed as thedrain, for conveniences only.

GATE ELECTRODE GT

The gate electrode GT is formed to project perpendicularly (i.e.,upward, as viewed in FIGS. 1 and 5) from the scanning signal lines GL(or branched in the "T-shape"), as shown in detail in FIG. 5 (presentinga top plan view showing the second conductive layer g2 and i-typesemiconductor layer AS of FIG. 1 only). The gate electrode GT isextended to the regions to be individually formed with the thin filmtransistors TFT1 and TFT2. These thin film transistors TFT1 and TFT2have their individual gate electrodes GT integrated (as their commongate electrode) to merge into the scanning signal line GL. The gateelectrode GT is constituted by the single level conductive layer g2. Thesecond conductive layer g2 is formed, for example, by sputteringaluminum (Al) in the thickness of about 1,000 to 5,500 angstroms. On thegate electrode GT, there is provided an anodized oxide film AOF of Al.

This gate electrode GT is made so slightly large as to cover thesemiconductor layer AS completely (as viewed upward), as shown in FIGS.1 and 2 and FIG. 5. In case, therefore, back lights BL such asfluorescent lamps are attached to the bottom of the substrate SUB1, thisopaque Al gate electrode GT establishes a shadow to shield thesemiconductor layer AS from the back lights, thus substantiallyeliminating the conducting phenomenon due to the optical irradiation,i.e., the deterioration of the OFF characteristics of the TFTs. Here,the intrinsic size of the gate electrode GT is given the least necessarywidth (including the positioning allowance of the gate electrode GT, thesource electrode SD1 and the drain electrode SD2) for extending betweenthe source and drain electrodes SD1 and SD2. The depth for determiningthat channel width W is determined in dependence upon the factor W/Ldetermining the mutual conductance gm, i.e., the ratio to the distance(i.e., the channel length) L between the source and drain electrodes SD1and SD2. The size of the gate electrode GT in the present liquid crystaldisplay device is naturally made larger than the aforementionedintrinsic size.

SCANNING SIGNAL LINE GL

The scanning signal line GL is constituted by the second conductive filmg2. The second conductive film g2 of the scanning signal line GL isformed at the same step as and integrally with the second conductivefilm g2 of the gate electrode GT. Moreover, the scanning signal line GLis also formed thereon with the anodized oxide film AOF of Al.

GATE INSULATING FILM GT

The insulating film GI is used as the individual gate insulating filmsof the thin film transistors TFT1 and TFT2. The insulating film GI isformed over the gate electrode GT and the scanning signal line GL. Theinsulating film GI is formed of, for example, a silicon nitride filmprepared by the plasma CVD, to have a thickness of 1,200 to 2,700angstroms (e.g., about 2,000 angstroms in the present liquid crystaldisplay device). The gate insulating film GI is formed to enclose theentirety of the matrix portion AR, as shown in FIG. 18, and to have itsperipheral portion removed to expose the external connection terminalsDTM and GTM to the outside.

i-TYPE SEMICONDUCTOR LAYER AS

The i-type semiconductor layer AS is used as the individual channelforming regions of the thin film transistors TFT1 and TFT2 divided intoa plurality of parts, as shown in FIG. 5. The i-type semiconductor layerAS is formed of an amorphous silicon film or polycrystalline siliconfilm to have a thickness of about 200 to 2,200 angstroms (e.g., about2,000 angstroms in the present liquid crystal display device).

This i-type semiconductor layer AS is formed subsequent to the formationof the Si₃ N₄ gate insulating film GI by changing the components ofsupply gases but by using the common plasma CVD system such that it isnot exposed from the system to the outside. On the other hand, anN(+)-type layer d0 (shown in FIG. 2) doped with 2.5% of phosphor (P) forthe ohmic contact is likewise formed subsequently to have a thickness ofabout 200 to 500 angstroms (e.g., about 300 angstroms in the presentliquid crystal display device). After this, the lower substrate SUB1 istaken out of the CVD system, and the N(+)-type layer d0 and the i-typeAS are patterned into independent islands by the photographictechnology, as shown FIGS. 1 and 2 and FIG. 5.

The i-type semiconductor layer As is also formed between theintersecting portions (or crossover portions) of the scanning signalline GL and the video signal line DL, as shown in FIGS. 1 and 5. Thiscrossover i-type semiconductor layer As is formed to reduce theshort-circuiting between the scanning signal line GL and the videosignal line DL at the intersecting portion.

TRANSPARENT PIXEL ELECTRODE ITO1

The transparent pixel electrode ITO1 constitutes one of the parts of apixel electrode of a liquid crystal display.

The transparent pixel electrode ITO1 is connected with both the sourceelectrode SD1 of the thin film transistor TFT1 and the source electrodeSD1 of the thin film transistor TFT2. Even if, therefore, one of thethin film transistors TFT1 and TFT2 become defective, a suitable portionmay be cut by a laser beam in case the defect invites an adverse action.Otherwise, the situation may be left as it is because the other thinfilm transistor is normally operating. Incidentally, both the two thinfilm transistors TFT1 and TFT2 scarcely become defective, and theprobability of the point defect or line defect can be drasticallyreduced by that redundant system. The transparent pixel electrode ITO1is formed of a first conductive film d1, which is made of a transparentconductive film (of Indium-Tin-Oxide, i.e., ITO or NESA film) to have athickness of 1,000 to 2,000 angstroms (e.g., about 1,400 angstroms inthe present liquid crystal display device).

SOURCE ELECTRODE SD1 AND DRAIN ELECTRODE SD2

The individual source electrodes SD1 and drain electrodes SD2 of thedivided thin film transistors TFT1 and TFT2 are formed over thesemiconductor layer AS and separately from each other, as shown in FIGS.1 and 2 and FIG. 6 (presenting a top plan view showing the layers d1 tod3 of FIG. 1 only).

Each of the source electrode SD1 and the drain electrode SD2 is formedby overlaying a second conductive film d2 and a third conductive film d3sequentially from the lower side contacting with the N(+)-typesemiconductor layer d0. These second conductive film d2 and thirdconductive film d3 of the source electrode SD1 are formed at the samefabrication step as those of the drain electrode SD2.

The second conductive film d2 is formed of a sputtered chromium (Cr)film to have a thickness of 500 to 1,000 angstroms (e.g., about 600angstroms in the present liquid crystal display device). The Cr film isformed to have a thickness no more than 2,000 angstroms because itestablishes a high stress if it is made excessively thick. The Cr filmhas an excellent contact with the N(+)-type semiconductor layer d0. TheCr film constitutes the so-called "barrier layer" preventing the Al ofthe third conductive film d3 described hereinafter from diffusing intothe N(+)-type semiconductor layer d0. The second conductive film d2 maybe made of not only the aforementioned Cr film but also a refractorymetal (e.g., Mo, Ti, Ta or W) film or its silicide (e.g., MoSi₂, TiSi₂,TaSi₂ or WSi₂).

The third conductive film d3 is formed by sputtering Al to have athickness of about 3,000 to 5,000 angstroms (e.g., about 4,000 angstromsin the present liquid crystal display device). The Al layer is lessstressed than the Cr layer so that it can be formed to have a largerthickness thereby to reduce the resistances of the source electrode SD1,the drain electrode SD2 and the video signal line DL. The thirdconductive film d3 may be formed of not only the pure Al film but alsoan Al film containing silicon or copper (Cu) as an additive.

After the second conductive film d2 and the third conductive film d3have been patterned with the same mask pattern, the N(+)-type layer d0is removed by using the same photographic mask or the second conductivefilm d2 and the third conductive film d3. Specifically, the N(+)-typelayer d0 left on the i-th layer AS is removed in self-alignment whileleaving the second conductive film d2 and the third conductive film d3as they are. Since, at the same time, the N(+)-type layer d0 is etchedto remove its whole thickness, the i-th layer AS is slightly etched offat its surface portion, but this removal may be controlled by theetching period.

The source electrode SD1 is connected with the transparent pixelelectrode ITO1. The source electrode SD1 is formed along the steppedshape (i.e., the step corresponding to the sum of the thicknesses of thesecond conductive film g2, the anodized oxide film AOF, the i-typesemiconductor layer AS and the N(+)-type semiconductor layer d0) of thei-type semiconductor layer AS. More specifically, the source electrodeSD1 is composed of the second conductive film d2 formed along thestepped shape of the i-type semiconductor layer AS and the thirdconductive film d3 formed over the second conductive film d2. This thirdconductive film d3 of the source electrode SD1 is formed to ride overthe i-type semiconductor AS, because the Cr film of the secondconductive film d2 cannot be made so thick because of the increase inthe stress as to ride over the stepped shape of the i-type semiconductorlayer AS. In short, the second conductive film d2 is made thick toimprove the step coverage. The third conductive film d3 can be madethick so that it can highly contribute to the reduction of theresistance of the source electrode SD1 (as well as those of the drainelectrode SD2 and the video signal line DL).

PASSIVATION FILM PSV1

Over the thin film transistor TFT and the transparent pixel electrodeITO1, there is formed the passivation film PSV1, which is providedmainly for protecting the thin film transistor TFT against humidity orthe Like. Thus, the passivation film PSV1 to be used is highlytransparent and humidity resistant. The passivation film PSV1 is formedof a silicon oxide film or silicon nitride film prepared by the plasmaCVD, to have a thickness of about 1 micron.

The passivation film PSV1 is formed, as shown in FIG. 18, to enclose theentirety the matrix portion AR and is removed at its peripheral portionto expose the external connection terminals DTM and GTM to the outsideand at the portion, in which the common electrode COM at he side of theupper substrate SUB2 is connected with the external connection terminalconnecting leading line INT of the lower substrate SUB1 by means of thesilver paste AGP. In connection with the thickness connection betweenthe passivation film PSV1 and the gate insulating film GI, the former ismade thick considering the passivation effect whereas the latter is madethin considering the mutual conductance gm of the transistor. As aresult, as shown in FIG. 18, the passivation film PSV1 having a highpassivation effect is made so larger than the gate insulating film GI asto have its peripheral portion passivated as wide as possible.

SHIELDING FILM BM

At the side of the upper substrate SUB2, there is disposed the shieldingfilm BM for shielding any external light (i.e., the light coming fromthe top of FIG. 2) from entering the i-type semiconductor layer AS to beused as the channel forming region, as hatched to have the pattern shownin FIG. 7. Here, FIG. 7 is a top plan view showing only the firstconductive layer d1 comprised of the ITO film, the filter layer FIL andthe shielding film BM of FIG. 1. The shielding film BM is formed of afilm having a high shielding property to the light, e.g., an aluminumfilm or chromium film. In the present liquid crystal display device, theshielding film BM is formed of a chromium film by the sputtering, tohave a thickness of about 1,300 angstroms.

As a result, the common semiconductor layer AS shared by the thin filmtransistors TFT1 and TFT2 is sandwiched between the upper shielding filmBM and the lower but larger gate electrode GT so that it is shieldedfrom the outside natural light or the back lights. The shielding film BMis formed around the pixel, as hatched in FIG. 6. Specifically, theshielding film BM is formed in a lattice (of black matrix) shape, whichdefines the effective display region of one pixel. As a result, thecontour of each pixel is clarified to improve the contrast by theshielding film BM. In other words, this shielding film BM has twofunctions, i.e., the shielding for the semiconductor layer AS and theblack matrix functions. Further, since the portion of the transparentpixel electrode ITO1 (at the lower righthand portion of FIG. 1) opposedto the foot of the rubbing direction is shielded from the light by theshielding film BM, even if a domain is induced at the above portion, thedisplay characteristics are hardly deteriorated because the domain isshaded.

Incidentally, the back lights may be attached to the side of the uppertransparent glass substrate SUB2, whereas the lower transparent glasssubstrate SUB1 may be disposed at the observation side (exposed to theoutside).

The shielding film BM is additionally formed at its peripheral portionwith a framed pattern, as shown in FIG. 17, which is formed to mergeinto the pattern of the matrix portion having a plurality of dot-shapedopenings, as shown in FIG. 7. The shielding film BM at the peripheralportion is extended to the outside of the seal portion SL, as shown inFIGS. 17 to 20, thereby to prevent the leakage light such as the lightreflected from an implemented machine such as a personal computer fromentering the matrix portion. On the other hand, the shielding film BM islimited to the inside of the edge of the substrate SUB2 within about 0.3to 1.0 mm and is formed to avoid the cut region of the substrate SUB2.

COLOR FILTER FIL

The color filter FIL is prepared by cooling a dyeing base, which is madeof a resin material such as an acrylic resin, with a dye. The colorfilter FIL is formed (as shown in FIG. 8) in the shape of stripe and ina position to face the pixel. (FIG. 8 shows the first conductive filmd1, the black matrix layer BM and the color filter layer FIL of FIG. 4only, and the B, G and R filters are hatched at 45 degrees and 135degrees and in a crossing manner, respectively.) The color filter FIL ismade slightly large to cover the pixel electrode ITO1 in its entirety,as shown in FIGS. 7 to 9. The shielding film BM is so formed inside ofthe peripheral edge of the pixel electrode ITO1 as to overlap the colorfilter FIL and the pixel electrode ITO1.

The color filter FIL can be formed in the following manner. First ofall, the dyeing base is formed on the surface of the upper transparentglass substrate SUB2, and the dyeing base other than that in the redcolor filter forming region is removed by the photolithographictechnology. After this, the dyeing base is dyed with the red dye andfixed to form the red filter R. Next, the green filter G and the fluefilter B are sequentially formed by the similar steps.

PASSIVATION FILM PSV2

The passivation film PSV2 is provided for preventing the dyes fordifferent colors of the color filter FIL from leaking into the liquidcrystal LC. The passivation film PSV2 is made of a transparent resinmaterial such as an acrylic resin or epoxy resin.

COMMON TRANSPARENT PIXEL ELECTRODE ITO2

The common transparent pixel electrode ITO2 is opposed to thetransparent pixel electrode ITO1, which is provided for each pixel atthe side of the lower transparent glass substrate SUB1, so that theliquid crystal LC has its optical state varied in response to thepotential difference (or electric field) between each pixel electrodeITO1 and the common pixel electrode ITO2. This common transparent pixelelectrode ITO2 is fed with the common voltage Vcom. In the presentembodiment, this common voltage Vcom is set at an intermediate potentialbetween a driving voltage Vdmin at the low level and a driving voltageVdmax at the high level, both of which are applied to the video signalline DL. An AC voltage may be applied in case the supply voltage of theintegrated circuit to be used in the video signal drive circuit is to bereduced to one half. Incidentally, the top plan shape of the commontransparent pixel electrode ITO2 should be referred to FIGS. 17 and 18.

GATE TERMINAL PORTION

FIG. 9 presents a connection structure from the scanning signal line GLof the display matrix to its external connection terminal GTM, and (A)is a top plan view whereas (B) is a section taken along line B--B of(A). Incidentally, FIG. 9 corresponds to the lower portion of FIG. 18,and the hatched line portions are shown by straight lines forconveniences.

Letters AO designate a photolithographic mask pattern, namely, a photoresist pattern for selective anodization. As a result, this photo resistis anodized and then removed so that the shown pattern AO is not left asa complete but as a trace because the oxide film AOF is selectivelyformed in the gate line GL, as shown in section. With reference to theboundary line AO of the photo resist in the top plan view, the lefthandside is the region which is covered with the resist and is not anodized,whereas the righthand side is the region which is exposed from theresist to the outside and is anodized. The anodized Al layer g2 has itssurface formed with its oxide Al₂ O₃ film AOF and its lower conductiveportion reduced in volume. Of course, the anodization is so carried outfor a proper time and at a proper voltage that the conductive portionmay be left. The mask pattern AO is made to intersect the scanning lineGL not in a straight line but in a folded crank shape.

The Al layer g2, as shown, is hatched for easy understanding, but theregion left non-anodized is patterned in a comb shape. This is intendedto suppress the probability of the line breakage and the sacrifice ofthe conductivity to the minimum while preventing any formation ofwhiskers by narrowing the width of each Al layer and bundling aplurality of them in parallel, because the whisker will occur in thesurface for the wide Al layers. In the present embodiment, therefore,the portion corresponding to the root of the comb is displaced along themask AO.

The gate terminal GTM is formed of: a Cr layer g1 having an excellentcontact with the silicon oxide SiO layer and a higher resistance togalvanic corrosion than Al or the like; and the transparent conductivelayer d1 protecting the surface of the Cr layer g1 and having the samelevel (belonging to the same layer and formed simultaneously) as thepixel electrode ITO1. Incidentally, the conductive layers d2 and d3formed over and on the sides of the gate insulating film GI are left asa result that the conductive layers g2 and g1 are covered with the photoresist so that they may not be etched off by pin holes or the like atthe time of etching the conductive layers d3 and d2. Moreover, the ITOlayer d1 extended rightward across the gate insulating film GI isprovided for further completing the similar counter-measures.

In the top plan view, the gate insulating film GI is formed at the morerighthand side than its boundary, and a passivation film PSV1 is alsoformed at the more righthand side than the boundary so that the terminalportion GTM at the lefthand side can be exposed from them into electriccontact with the external circuits. Although only one pair of the gateline GL and the gate terminal is shown, a plurality of pairs arearranged vertically in FIG. 18, as a matter of fact, to constitute theterminal group Tg (as shown in FIGS. 17 and 18), and the gate terminalshave their lefthand ends are extended in the fabrication process acrossthe cut region CT1 of the substrate and are short-circuited by a lineSHg. This short-circuiting line SHg in the fabrication process is usefulfor supplying the electric power at the anodizing time and forpreventing the electrostatic breakdown at the time of rubbing theorientation film ORI1.

DRAIN TERMINAL DTM

FIG. 10 is a diagram showing the connection from the video signal lineDL to its external connection terminal DTM, and (A) presents a top planview whereas (B) presents a section taken along line B--B of (A).Incidentally, FIG. 10 corresponds to the upper righthand portion of FIG.18 and has its righthand direction corresponding to the upper endportion (or the lower end portion) of the substrate SUB1, although thedirection of the drawing is changed for conveniences.

Letters TSTd designate a test terminal which is not connected with anyexternal terminal but widened to contact with a probe or the like.Likewise, the drain terminal DTM is also made wider than the wiringportion as to connected with the external terminal. The test terminalTSTd and the external connection drain terminal DTM are so alternatelyarrayed in plurality as to be vertically staggered so that the testterminal TSTd terminates without reaching the end portion of thesubstrate SUB1, as shown. But, the drain terminals DTM constitute theterminal group Td (whose suffix is omitted), as shown in FIG. 18, andare further extended across the cut line CT1 of the substrate SUB1 sothat all of them are short-circuited to each other through lines SHd soas to prevent any electrostatic breakdown during the fabrication step.The drain connection terminals are connected to the opposite sides ofthe video signal lines DL, in which the test terminal TSTd are present,across the matrix, whereas the test terminals are connected to theopposite sides of the video signal lines DL, in which the drainconnection terminals DTM are present, across the matrix.

By a reason similar to the gate terminal GTM, the drain connectionterminal DTM is formed of two layers, i.e., the Cr layer g1 and the ITOlayer d1 and is connected with the video signal line DL through theportion, from which is removed the gate insulating film GI. Thesemiconductor layer AS formed over the end portion of the gateinsulating film GI is provided for etching the edge of the gateinsulating film GI in a taper shape. For connection with an externalcircuit, the passivation film PSV1 is naturally removed from theterminal DTM. Letters AO designate the aforementioned anodizing maskwhich has its boundary formed to enclose the entirety of the matrix. Asshown, the lefthand side is covered with the mask, but the remaininguncovered portion has no layer g2 so that it has no relation to thepattern.

The leading lines from the matrix portion to the drain terminal portionDTM are constructed, as shown at (C) in FIG. 19, such that the layers d2and d3 at the same level as the video signal lines DL are laminatedmidway of the seal pattern SL just over the layers d1 and g1 at the samelevel as the drain terminal portion DTM. This construction is intendedto minimize the probability of breakage of lines thereby to protect thegalvanically corrosive Al layer as much as possible with the passivationfilm PSV1 and the seal pattern SL.

STRUCTURE OF LATCHING CAPACITOR CADD

The transparent pixel electrode ITO1 is formed to overlap the adjoiningscanning signal line GL at the end opposed to the end to be connectedwith the thin thin film transistor TFT. This superposition constitutes alatching capacity element (or an electrostatic capacity element)Caddwhich uses the transparent pixel electrode ITO as its one electrode PL2and the adjoining scanning signal line GL as its other electrode PL1, asis apparent from FIGS. 1 and 3. This latching capacity element Cadd hasits dielectric films formed of: the insulating film GI used as the gateinsulating film of the thin film transistor TFT; and the anodized filmAOF.

The latching capacitor Cadd is formed in the widened portion of thesecond conductive layer g2 of the scanning gate line GL, as is apparentfrom FIG. 5. Here, the second conductive film g2 at the portionintersecting the video signal line DL is thinned to reduce theprobability of the short-circuiting with the video signal line DL.

Even if the transparent pixel electrode ITO1 is broken at the steppedportion of the electrode PL1 of the latching capacitor Cadd, its defectis compensated by the island region which is constructed of the secondconductive film d2 and the third conductive film d3 formed across thatstep.

EQUIVALENT CIRCUIT OF WHOLE DISPLAY CIRCUIT

FIG. 11 shows an equivalent circuit diagram of the display matrixportion and a wiring diagram of its peripheral circuits. Although thisdrawing is a circuit diagram, it is depicted in a manner to correspondto a practical geometric disposition. Letters AR designate a matrixarray formed by disposing a plurality of pixels two-dimensionally.

In the drawing, letter X designates the video signal line, and suffixesG, B and R are added to correspond to green blue and red pixels,respectively. Letter Y designates the scanning signal line GL, andsuffixes 1, 2, 3, , and so on are added in accordance with the sequenceof the scanning timing.

The video signal line X (whose suffix is omitted) is alternatelyconnected with the upper (or odd-numbered) video signal driving circuitHe and with the lower (or even-numbered) video signal driving circuitHo.

The scanning signal line Y (whose suffix is omitted) is connected with avertical scanning circuit V.

Letters SUP designate a circuit which includes a power supply circuitfor obtaining a plurality of divided and stabilized voltage sources fromone voltage source, and a circuit for converting data for CRT (i.e.,Cathode Ray Tube) from a host (i.e., a higher-order operationalprocessor) to data for the TFT liquid crystal display device.

EQUIVALENT CIRCUIT OF LATCHING CAPACITOR CADD AND ITS OPERATIONS

The equivalent circuit of the pixel shown in FIG. 1 is shown in FIG. 12.In FIG. 12, letters Cgs designate a parasitic capacitor to be formedbetween the gate electrode GT and the source electrode SD1 of the thinfilm transistor TFT. The parasitic capacitor Cgs has its dielectric filmmade of the insulating film GT and the anodized oxide film AOF. LettersCpix designate a liquid crystal capacitor to be formed between thetransparent pixel electrode ITO1 (or PIX) and the common transparentpixel electrode ITO2 (or COM). The dielectric film of the liquid crystalcapacitor Cpix is formed of the liquid crystal LC<the passivation filmPSV1 and the alignment films ORI1 and ORI2. Letters Vlc designate a midpoint potential.

The latching capacity element Cadd functions to reduce the influences ofthe gate potential variation delta Vg upon the center potential (e.g.,the pixel electrode potential) Vlc when the thin film transistor TFTswitches, as expressed by the following formula:

    delta Vlc={Cgs/(Cgs+Cadd+Cpix)}x deltaVg,

wherein delta Vlc indicates the variation of the central potential dueto delta Vg. This variation delta Vlc causes the DC component to beadded to the liquid crystal LC and can be reduced the more for thehigher latching capacitor Cadd. Moreover, the latching capacitor Caddfunctions to elongate the discharge time and stores the videoinformation for a long time after the thin film transistor TFT is turnedoff. The DC component to be applied to the liquid crystal LC can improvethe lifetime of the liquid crystal LC, to reduce the so-called"printing", by which the preceding image is left at the time ofswitching the liquid crystal display frame.

Since the gate electrode GT is enlarged to such an extent as to coverthe semiconductor layer AS completely, as has been describedhereinbefore, the overlapped area with the source electrode SD1 and thedrain electrode SD2 is increased to cause an adverse effect that theparasitic capacity Cgs is increased to make the center potential Vlcliable to be influenced by the gate (scanning) signal Vg. However, thisdemerit can be eliminated by providing the latching capacitor Cadd.

The latching capacity of the latching capacitor Cadd is set from thepixel writing characteristics to a level four to eight times as large asthat of the liquid crystal capacity Cpix (4*Cpix<Cadd<8*Cpix) and eightto thirty two times as large as that of the capacity Cgs(8*Cgs<Cadd<32*Cgs).

METHOD OF CONNECTING ELECTRODE LINE OF LATCHING CAPACITOR CADD

The initial stage scanning signal line GL (i.e., Y₀) to be used only asthe capacity electrode line is set to the same potential as that of thecommon transparent pixel electrode (Vcom) ITO2, as shown in FIG. 11. Inthe example of FIG. 18, the initial stage scanning signal line isshort-circuited to the common electrode COM through the terminal GTO,the leading line INT, a terminal DTO and an external line.Alternatively, the initial stage latching capacity electrode line Y₀ maybe connected with the final stage scanning signal line Yend or a DCpotential point (or AC ground point) other than the Vcom, or connectedto receive one excess scanning pulse Y₀ from the vertical scanningcircuit V.

STRUCTURE FOR CONNECTION WITH EXTERNAL CIRCUIT

FIG. 21 is a diagram showing a sectional structure of the tape carrierpackage TCP, in which the integrated circuit chip CHI is mounted on theflexible wiring substrate (as called "TAB": Tape Automated Bonding), toconstruct the scanning signal driving circuit V or the video signaldriving circuits He and Ho. FIG. 22 is a section showing the state of anessential portion, in which the tape carrier package TCP is connected inthe present example with the video signal circuit terminal DTM.

In the same drawing, letters TTB designate an input terminal/wiringportion of the integrated circuit CHI, and letters TTM designate anoutput terminal/wiring portion of the integrated circuit CHI. Theseportions are made of Cu, for example, and have their individual innerleading end portions (as called the "inner leads") connected with abonding pad PAD of the integrated circuit CHI by the so-called"faced-down bonding method". The terminals TTB and TTM have their outerleading end portions (as called the "outer leads") corresponding to theinput and output of the semiconductor integrated circuit chip CHI,respectively, and are connected with the CRT/TFT converter circuit andthe power supply circuit SUP by the soldering method and with the liquidcrystal display F, panel PNL through an anisotropic conductive film ACF.The package TCP is so connected with the panel that its leading endportion covers the passivation film PSV1 having the connection terminalDTM exposed at the side of the panel PNL. As a result, the externalconnection terminal DTM (GTM) is strong against the galvanic corrosionbecause it is covered with at least one of the passivation film PSV1 orthe package TCP.

Letters BF1 designate a base film made of polyimide or the like, andletters SRS designate a solder resist film for masking to prevent thesolder from leaking to an unnecessary portion at the soldering time. Thegap between the upper and lower glass substrates outside of the sealpattern SL is protected after the rinsing step by the epoxy resin EPX orthe like, and this protection is multiplexed by filling a silicone resinSIL between the package TCP and the upper substrate SUB2.

MANUFACTURING PROCESS

Next, a process for manufacturing the side of the substrate SUB1 of theaforementioned liquid crystal display device will be described withreference to FIGS. 13 to 15. In these Figures, the central lettersindicate the abbreviations of the step names, and the lefthand sides.show the pixel portions shown in FIG. 2 whereas the righthand sidesshow the process flow, as viewed in section from the vicinity of thegate terminals shown in FIG. 9. Steps A to I excepting Step D aredivided to correspond to the individual photolithographic steps, and anysections of the individual steps indicate the steps, at which the photoresists are removed after the photolithographic treatments.Incidentally, these photolithographic treatments are intended in thepresent description to imply a series of operations from the applicationof a photo resist to the development through a selective exposure usinga mask, and their repeated description will be omitted. The descriptionwill be made in accordance with the steps divided, as follows.

STEP A, FIG. 13

A silicon dioxide film SIO is deposited by the dip treatment on bothsurfaces of a lower transparent glass substrate SUB1 made of 7059 glass(under the trade name), and then a baking is carried out at 500 degreefor 60 minutes. A first conductive film g1 consisting of a 1,100angstrom-thick chromium film is deposited on the lower transparent glasssubstrate SUB1 by the sputtering. After the photolithographic treatment,the first conductive film g1 is etched selectively by the photoetchingusing a ceric ammonium nitrate solution as an etching solution, therebyforming a gate terminal GTM and a drain terminal DTM and forming also apower bus line SMg for anodization for connecting the gate terminal GTM,and a pad (although not shown) connected with the power bus line SHg foranodization.

STEP B, FIG. 13

A second conductive film g2 having a thickness of 2,800 angstroms andmade of Al-Pd, Al-Si, Al-Si-Ti or Al-Si-Cu is formed by the sputtering.After the photolithographic treatment, the second conductive film g2 isselectively etched with a mixed acid solution of phosphoric acid, nitricacid and glacial acetic acid.

STEP C, FIG. 13

After the photolithographic treatment (i.e., after the formation of theaforementioned anodized mask AO), the substrate SUB1 is dipped in theanodizing liquid which is prepared by diluting a solution containing 3%of tartaric acid adjusted to PH 6.2 to 6.3 with a solution of ethyleneglycol, and the anodizing current density is adjusted to 0.5 mA/cm² (foranodization at a constant current). Next, an anodization is carried outtill an anodization current of 125 V necessary for a predetermined Al₂O₃ film thickness is reached. After this, the substrate SUB1 isdesirably held in this state for several ten minutes (for anodization ata constant voltage). This is important for achieving a uniform Al₂ O₃film. Thus, the conductive film g2 is anodized to form an anodized filmAOF having a thickness of 1,800 angstroms over the scanning signal lineGL, the gate electrode GT and the electrode PL1.

STEP D, FIG. 14

Ammonia gas, silane gas and nitrogen gas are introduced into a plasmaCVD apparatus to form a Si nitride film having a thickness of 2,000angstroms, and silane gas and hydrogen gas are introduced into theplasma CVD apparatus to form an i-type amorphous Si film having athickness of 2,000 angstroms. After this, hydrogen gas and phosphine gasare introduced into the plasma CVD apparatus to form an N(+)-typeamorphous Si film having a thickness of 300 angstroms.

STEP E, FIG. 14

After the photolithography, the N(+)-type amorphous Si film and thei-type amorphous Si film are selectively etched by the photoetchingusing SF₆ and CCl₄ as the dry etching gas to form an island of an i-typesemiconductor layer AS.

STEP F, FIG. 14

After the photolithography, the Si nitride film is selectively etched byusing SF₆ as the dry etching gas.

STEP G, FIG. 15

A first conductive film d1 formed of an ITO film having a thickness of1,400 angstroms is formed by the sputtering. After the photolithography,the first conductive film d1 is selectively etched by using a mixed acidsolution of hydrochloric acid and nitric acid as the etching solution,to form the uppermost layer of the gate electrode GTM and the drainterminal DTM and the transparent pixel electrode ITO1.

STEP H, FIG. 15

A second conductive film d2 of Cr having a thickness of 600 angstroms isformed by the sputtering, and a third conductive film d3 of Al-Pd,Al-Si, Al-Si-Ti or Al-Si-Cu having a thickness of 4,000 angstroms isformed by the sputtering. After the photolithography, the thirdconductive film d3 is etched by a solution similar to that of Step B,and the second conductive film d2 is etched by a solution similar tothat of Step A, to form the video signal line DL, the source electrodeSD1 and the drain electrode SD2. Next, CCl₄ and SF₆ are introduced intoa dry etching apparatus to etch the N(+)-type amorphous Si film therebyto remove the N(+)-type semiconductor layer d0 selectively from betweenthe source and the drain.

STEP I, FIG. 15

Ammonia gas, silane gas and nitrogen gas are introduced into a plasmaCVD apparatus to form a Si nitride film having a thickness of 1 micron.After the photolithography, the Si nitride film is selected by thephotoetching technique using SF₆ as the dry etching gas, to form thepassivation film PSV1.

STRUCTURE OF WHOLE LIQUID CRYSTAL DISPLAY MODULE

FIG. 23 is an exploded perspective view showing a liquid crystal displaymodule MDL, and the specific construction of the individual componentsis shown in FIGS. 24 to 39.

Letters SHD designate a shield casing (=metal frame) made of a metalplate; letters LCW designate a liquid crystal display window; lettersPNL designate a liquid crystal display panel; letters SPB designate anoptical diffusion plate; letters MFR designate a middle frame; lettersBL designate back lights; letters BLS designate a back light support;and letters LCA designate a lower casing. All of these members arestacked in vertical positions, as shown, to assemble a module MDL.

The module MDL is constructed of three kinds of holding members: thelower casing LCA, the middle frame MFR, and the shield casing SHD. Thesethree members are individually formed generally into box shapes and arestacked in the recited order to hold the remaining two members mountingthe individual parts by the shield casing SHD.0 The display panel PNLand the optical diffusion board SPB can be once placed on the middleframe MFR, and the back light support BLS supporting the four backlights (or cold-cathode fluorescent lamps) can be once placed on thelower casing LCA. As a result, the two members, i.e., the lower casingLCA and the middle frame MFR can be stacked without any upside-downwhile packaging the necessary parts, so that the manufacture can befacilitated to provide a device having an excellent assembly and a highreliability. This advantage is one of the major features of the presentmodule.

The individual members will be described in more detail in thefollowing.

SHIELD CASING SHD

FIG. 24 presents the upper side, front side, rear side, righthand sideand lefthand side of the shield casing SHD, and FIG. 25 is a perspectiveview showing the shield casing SHD obliquely downward.

The shield casing (or metal frame) SHD is fabricated by punching orfolding a metal sheet by the pressing technique.. Letters LCW designatea window for exposing the display panel PNL to the field of view, aswill be called the "display window".

Letters CL designate (totally nineteen) fixing pawls for the middleframe MFR, and letters FK designate (totally nine) fixing hooks for thelower casing LCA. These pawls and hooks are integrated with the shieldcasing SHD. The fixing pawls CL in the shown state are individuallyfolded inward, at the assembly, and inserted into the square fixing pawlholes CLH (as shown in the individual side views of FIG. 27) formed inthe middle frame MFR. As a result, the shield casing SHD holds themiddle frame MFR for holding/implementing the display panel PNL and soon so that they are firmly fixed. The fixing hooks FK are individuallyfitted in fixing projections FKP (as shown at the individual side viewsof FIG. 34), which are formed on the lower casing LCA. As a result, theshield casing SHD holds the lower casing LCA, in which the back lightsBL and the back light support BLS are held and implemented, so that theyare firmly fixed together. Incidentally, the middle frame MFR and thelower casing LCA are fitted at their peripheral edges, and the shieldcasing SHD is fitted to cover the middle frame MFR, so that these threemembers are integrated. Moreover, the display panel PNL is equipped onits upper and lower faces with a thin rubber spacer (or rubber cushion,although not shown) having an elongated rectangular shape on its fourside edges exerting no influence upon the display. The upper side rubberspacer is sandwiched between the display panel PNL and the shield casingSHD, and the lower rubber spacer is sandwiched between the display panelPNL and the middle frame MFR and the optical diffusion plate SPB. Bypushing the shield casing SHD into the device by making use of theelasticity of those rubber spacers, the fixing hooks FK are caught bythe fixing projections FKP so that the two fixing members function asstoppers. Moreover, the fixing pawls CL are folded and inserted into thepawl holes CLE, and the middle frame MFR and the lower casing LCA arefixed by the shield casing SHD so that the whole module is firmly heldin its entirety without any necessity for other fixing members. As aresult, the assembly can be facilitated to drop the fabrication cost.Moreover, the mechanical strength can be increased to improve theresistance to vibrations and the reliability of the device. Since,moreover, the fixing pawls CL and the fixing hooks FK can be easilyremoved (merely by folding back the fixing pawls CL and removing thefixing hooks FK), the three members can be easily disassembled andassembled with easy repair and replacement of the back lights BL (Here,the fixing hooks FK of the lower casing LCA to be more frequentlyremoved for the back light replacement are made more easily removable).Here, in the present module, the lower casing LCA and the middle frameMFR are fixed not only by the aforementioned fixing members but also byfastening the screws into four through screw holes LHL (as shown inFIGS. 34 to 36) formed in the lower casing LCA and four screw holes MVH(as shown in FIG. 28) of the middle frame MFR.

Letters COH designate common through holes. Two common through holes COHare commonly formed not only in the shield casing SHD but also a drivecircuit substrate PCB1 of the display panel PNL, a drive circuitsubstrate PCB2 of the middle frame MFR, in the midddle frame MFR and inthe lower casing LCA. The relative positions of the individual membersand parts are precisely set by implementing them such that theindividual common through holes COH are inserted at the fabrication timesequentially from the lower casing LCA onto the pins which are anchoredin positions. Moreover, the common through holes COH can be used as thepositioning references when the module MDL is to be packaged in anapplication product such as the personal computer.

In the prior art, on the other hand, there is a problem that undesirableradiation electric waves for causing the EMI (i.e., Electro MagneticInterference) are emitted from the liquid crystal display device.

In the present invention, at least one of the divided circuit substratesis equipped with a frame ground pad, and this frame ground pad isconnected with a projection which is formed integral with the metallicshield casing. As a result, the ground line in the high-frequency rangecan be strengthened to suppress the establishment of the undesiredradiation electric waves. Specifically, as shown in FIG. 24, letters FGdesignate six frame grounds which are integrated with the metallicshield casing SHD. The frame grounds FG are formed of the "U-shaped"openings in the shield casing SHD, namely, elongated projectionsextending in the square openings. These thin projections areindividually folded inward the device and are connected by solder withthe frame ground pads FGP (as shown in FIG. 26), which in turn areconnected with the ground lines of the drive circuit substrate PCB1 ofthe display panel PNL.

DISPLAY PANEL PNL AND DRIVE CIRCUIT SUBSTRATE PCB1

FIG. 26 is a top plan view showing the state in which the drive circuitis implemented in the display panel PNL shown in FIGS. 16 and so on.

Letters CHI designate drive IC chips (of which: the lower three are thedrive IC chips at the vertical scanning circuit side whereas therighthand and lefthand six are the drive IC chips at the video signaldrive circuit side) for driving the display panel PNL. Letters TCPdesignate tape carrier packages in which are packaged the driving ICchips CHI by the tape automated bonding method (TAB), as has beendescribed with reference to FIGS. 21 and 22, and letters PCB1 designatedrive circuit substrates divided into three and made of PCB (i.e.,Printed Circuit Boards) in which are individually implemented the tapecarrier packages TCP and capacitors CDS. Letters FGP designate frameground pads. Letters FC designate flat cables for connecting the lowerside drive circuit substrate PCB1 and the lefthand side drive circuitsubstrate PCB1, and the lower side drive circuit substrate PCB1 and therighthand side drive circuit substrate PCB1 electrically. The flatcables FC to be used are prepared by sandwiching and supporting, asshown, a plurality of lead lines (made of phosphor bronze plated withSn) between the striped polyethylene layer and polyvinyl alcohol layer.

DRIVE CIRCUIT SUBSTRATE PCB1

The drive circuit substrate PCB1 is divided, as shown in FIG. 26, intothree, which are arranged in a shape of letter "U" around the displaypanel PNL and individually connected electrically and mechanicallythrough the two flat cables FC. Since the drive circuit substrate PCB1is divided, the stress, which is established in the longitudinaldirection of the drive circuit substrate PCB1 due to the difference inthe coefficients of thermal expansion between the display panel PNL andthe drive circuit substrate PCB1, can be absorbed at the flag cables FCto prevent any peel of the output leads (e.g., TTM of FIGS. 21 and 22)of the tape of the take carrier package TCP having a weak connectionstrength and the external connection terminal DTM (or GTM) of thedisplay panel, thereby to improve the reliability of the module againstthe heat. According to this substrate dividing method, moreover, thesingle substrate material can be divided into a number of sheets ofsubstrate PCB1 because of their simple shape so that the usingefficiency of the print substrate material is better than that of thesingle "U-shaped" substrate. Thus, there can be achieved an effect toreduce the costs for the parts and materials (to about 50% in case ofthe present embodiment. Incidentally, the drive circuit substrate PCB1can enhance the lead peel preventing effect better if it is made of asoft FPC (i.e., Flexible Printed Circuit) in place of the PCB, becausethe FPC is flexible. Moreover, an undivided integral "U-shaped" PCBcould be used. If this case, there can be achieved an effect ofenhancing the reliability by reducing the step number, by simplifyingthe control of the fabrication process due to the reduction of the partnumber, and by eliminating the connection cable between the PCBs.

The frame ground pads FGP, which are connected with each ground line ofeach of the three divided drive circuit substrates PCB1, are providedtotally in six because they are two for each substrate, as shown in FIG.26. In case the drive circuit substrate PCB1 is divided into plurality,no electric problem will arise if at least one of the divisions of thedrive circuit substrate is connected in respect of the DC current withthe frame ground. If the number of divisions is small in thehigh-frequency range, a potential for generating the undesired radiationelectric waves for causing the EMI (i.e., Electro Magnetic Interference)will be increased by the reflection of electric signals and thedeflection of the potential of the ground lines due to the difference inthe characteristic impedance between the divided individual drivecircuit substrates. Especially, the module MDL using the thin filmtransistors finds it difficult to counter-measure the EMI because ituses a high-speed clock. In order to prevent the EMI, the ground line(at the AC ground potential) is connected in at least one portion, e.g.,two portions in the present embodiment for each of the plurality ofdivided drive circuit substrates PCB1 with a common frame (i.e., theshield casing SHD) having a sufficiently low impedance. As a result, theground line is strengthened in the high-frequency range, an improvementof 5 dB or more in terms of the field intensity of the radiation can beobserved in case of the six connected portions of the presentembodiment, as compared with the case in which totally one portion isconnected with the shield casing SHD.

The frame grounds FG of the shield casing SHD are made of thin metalprojections so that they can be easily connected with the frame groundpads FGP of the display panel PNL by folding them, thus requiring nospecial wire (or lead) for the connections. Moreover, the shield casingSHD and the drive circuit substrate PCB1 can also be mechanicallyconnected through the frame grounds FG, to improve the mechanicalstrength of the drive circuit substrate PCB1.

MIDDLE FRAME MFR

FIG. 27 presents the upper side, front side, rear side, righthand sideand lefthand side of the middle frame MFR; FIG. 28 presents a bottomside of the middle frame; and FIG. 29 is a perspective view taken fromthe top side of the middle frame MFR.

The middle frame MFR is a member for holding the liquid crystal displayLCD, the optical diffusion board and the L-shaped drive circuitsubstrate PCB2, which are integrated with the drive circuit substratePCB1.

Letters BLW designate a back light window for introducing the light ofthe back lights BL into the liquid crystal display LCD and forplacing/holding the optical diffusion board SPB. Letters SPBS designatea portion for holding the optical diffusion board SPB. Letters RDWdesignate radiation holes, and letters CW designate notches forconnectors to be connected with the outside. Letters MVH designate fourscrew holes for fixing the lower casing LCA and the middle frame MFRtherethrough and through the through holes LHL (as shown in FIGS. 34 to36) of the lower casing LCA by means of not-shown screws. Letters CLHdesignate fixing holes (as shown in the individual side views of FIG. 27and in FIG. 29), into which are inserted the fixing pawls CL of theshield casing SHD. Letters 2HL designate fixing holes of the drivecircuit substrate PCB2 (as shown in FIG. 30), into which are insertedfixing members such as nylon rivets. The L-shaped drive circuitsubstrate PCB2 is arranged in the L-shaped region of the righthand andlower edges of the top plan view of the middle frame MFR of FIG. 27.Incidentally, the middle frame MFR is made of a synthetic resin in thesame white color as that of the back light support BLS and the lowercasing LCA. Moreover, since the middle frame MFR is made of thesynthetic resin, it is advantageous in the insulations of the drivecircuit substrate PCB1 and the drive circuit substrate PCB2.

OPTICAL DIFFUSION PLATE SPB

The optical diffusion board SPB (as shown in FIG. 23) is held on theholding portion SPBS (which is lower than the upper face of the middleframe MFR, as shown in FIGS. 27 and 29) which is provided on the fourperipheral edge portions of the back light window BLW of the middleframe MFR. If the optical diffusion board SPB is placed on the holdingportion SPBS, the optical diffusion board SPB and the middle frame MFRhave their upper faces located in a common plane. On the opticaldiffusion board SPB, there is placed the liquid crystal display LCDwhich is integrated with the drive circuit substrate PCB1. Between theliquid crystal display I,CD and the optical diffusion board SPB, thereis sandwiched the four rubber spacers (although not shown but should bereferred to the column of Shield Casing SHD), which are arranged on thefour peripheral edges of the lower side of the liquid crystal displayLCD, to seal up the liquid crystal display LCD and the optical diffusionboard SPB. Specifically, the optical diffusion board SPB is placed onthe middle frame MFR (or frame) whereas the optical diffusion board SPBhas its upper face covered with the liquid crystal display LCD, so thatthe liquid crystal display LCD and the optical diffusion board SPB havetheir gap sealed up completely with the rubber spacers (that is, theoptical diffusion board SPB and the liquid crystal display LCD areintegrated and fixed independently of the back light portion by means ofthe middle frame MFR). This construction can suppress the problems thata foreign substance may invade into the gap between the liquid crystaldisplay LCD and the optical diffusion plate SPB, and that a foreignsubstance caught electrostatically by a portion other than the displayregion may move to the display region to drop the display quality.Incidentally, the optical diffusion board SPB is so thicker than theoptical diffusion sheet as to prevent the foreign substance from beingoutstanding at the lower side of the optical diffusion board SPB.Moreover, the foreign substance present at the lower side of the opticaldiffusion board SPB is so far from the liquid crystal display LCD as tobecome reluctant to be focused. The image is diffused to raise noproblem. Still moreover, the construction is excellent because theoptical diffusion board SPB and the liquid crystal display LCD aresequentially held on the middle frame MFR.

DRIVE CIRCUIT SUBSTRATE PCB2

FIG. 30 presents the lower side of the drive circuit substrate PCB2. Thedrive circuit substrate PCB2 of the liquid crystal display LCD to beheld and mounted in the middle frame MFR is formed into an L-shape, asshown in FIG. 30, to implement electronic parts such as ICs, capacitorsor resistors. In this drive circuit substrate PCB2, there are mounted apower supply circuit for achieving a plurality of divided stable voltagesources from one voltage source and a circuit including a circuit forconverting data for CRT (i.e., Cathode Ray Tube) from a host (i.e., ahigher-order operational processor) to data for the TFT liquid crystaldisplay device. Letters CJ designate a connector connection portion tobe connected with a not-shown connector to be connected with theoutside. Incidentally, the drive circuit substrate PCB2 and the drivecircuit substrate PCB1 are electrically connected, as shown in FIG. 31,by the flat cable FC (as will be described in detail hereinafter).Moreover, the drive circuit substrate PCB2 and the inverter circuitsubstrate IPCB are electrically connected through the connector holesCHL (as shown in FIGS. 27 to 29), which are formed in the middle frameMFR, by the not-shown back light connector and back light cable whichare connected with the back light connection portion BC2 of the drivecircuit substrate PCB2 and the back light connection portion BCI of theinverter circuit substrate IPCB.

ELECTRIC CONNECTION BETWEEN DRIVE CIRCUIT SUBSTRATE PCB1 AND DRIVECIRCUIT SUBSTRATE PCB2

FIG. 31 presents the upper side showing the connection state between thedrive circuit substrate PCB1 (whose upper side is seen) of the liquidcrystal display LCD and the drive circuit substrate PCB2 (whose lowerside is seen) of the middle frame MFR.

The liquid crystal display LCD and the drive circuit substrate PCB2 areelectrically connected through the foldable flat cables FC. In thisstate, the operation check can be accomplished. The drive circuitsubstrate PCB2 is arranged over the lower side of the liquid crystaldisplay LCD by bending the flat cables FC by 180 degrees and is fittedin a predetermined recess of the middle frame MFR until it is fixed byfixtures such as nylon rivets. On the drive circuit substrate PCB2,there is placed and held the drive circuit substrate PCB1 which isintegrated with the liquid crystal display LCD.

BACK LIGHT SUPPORT BLS

FIG. 32 presents the upper side, rear side, righthand side and lefthandside of the back light support BLS, and FIG. 33 is a perspective viewshowing the back light support BLS from its upper side. The back lightsupport BLS supports the four back lights (i.e., cold-cathodefluorescent lamps) BL (as shown in FIGS. 37 and 23). Letters SPCdesignate a hole (or space), and the back light support BLS forms aframe.

The back light support BLS supports the four back lights BL throughwhite silicone rubbers SG (as shown in FIGS. 37 and 39). Letters SSdesignate a back light support for supporting the two ends of each backlight BL through the silicone rubbers SG. Incidentally, the siliconerubbers SG function to prevent any foreign substance from stealing intothe lighting regions of the back lights BL. Letters RH designate leadholes through which are guided leads LD (as shown in FIG. 37) connectedwith the two ends of the back lights BL.

Letters SHL designate four through holes formed in the back lightsupport BLS. These through holes SHL are aligned with the screw holesLVH of the lower casing LCA and are fixed in the lower casing LCA bymeans of not-shown screws.

Letters SRM designate back light reflectors which are formed on therighthand and lefthand inner sides of the back light support BLS of FIG.32 for reflecting the back lights BL (i.e., the outer two BL of the fourback lights BL). Like the upper sides of the back light reflectors RM(as shown in FIGS. 34 and 36), the back light reflectors SRM areconstructed of a combination of a plurality of planes for reflecting thelights of the back lights BL efficiently toward the liquid crystaldisplay LCD (as should be referred to the description of Lower Casing).Incidentally, the back light support BLS is molded of a synthetic resinin the same white color as that of the middle frame MFR and the lowercasing LCA.

According to the embodiment of the present invention, moreover, the backlight support for supporting the back lights are provided separately ofthe casings of the back lights the leads of the back lights can besoldered to the inverter circuit substrate while being supported by theback light supports, before the back lights are fixed in its casing.Thus, the working efficiency is excellent, and the replacement ofdefective parts is easy.

LOWER CASING LCA

FIG. 34 presents the upper side (or reflecting side), rear side,righthand side and lefthand side of the lower casing LCA; FIG. 35presents the lower side of the lower casing LCA; FIG. 36 is aperspective view showing the lower casing LCA from its upper side; andFIG. 38 is a section (taken along line 38--38 of FIG. 34) showing thelower casing LCA.

The lower casing LCA is a holding member (or back light mounting casing)for the back lights BL, the back light support BLS, and an invertercircuit substrate IPCB for lighting the back lights BL. The lower casingLCA acts as the reflectors for the back lights BL and is integrallymolded of a synthetic resin in white or a color capable of reflectingthe lights of the back lights BL the most efficiently. The lower casingLCA is formed on its upper face with three back light reflectors RMwhich are made integral with the Lower casing LCA to provide thereflecting faces of the back lights BL. The three back light reflectorsRM are composed of a combination of a plurality of planes for reflectingthe lights of the back lights BL efficiently toward the liquid crystaldisplay LCD. Specifically, the back light reflectors RM have sectionscontoured by straight lines which are approximated from curves computedto reflect the lights of the back lights BL the most efficiently.Incidentally, the back light reflectors RM are higher than the upperfaces of the back lights BL so as to increase the reflectivities (asshown in FIG. 9). Since the casing for and the reflectors of the backlights BL are thus constructed of the integral member, the number ofparts can be reduced to simplify the structure and to drop thefabrication cost. Thus, it is possible to improve the vibrational shockresistance and thermal shock resistance of the device and to improve thereliability of the device. Since the lower casing LCA is made of asynthetic resin, it is advantageous in the insulation of the invertercircuit substrate IPCB.

Incidentally, letters LVH designate four screw holes, and the back lightsupport BLS is fixed in the lower casing LCA through those screw holesLVH and the through holes SHL (as shown in FIGS. 32 and 33) of the backlight support BLS by means of the not-shown screws. Letters LHLdesignate four through holes, and the middle frame MFR and the lowercasing LCA are fixed through those through holes LHL and the screw holesMVH (as shown in FIG. 28) of the middle frame MFR by means of thenot-shown screws. Letters IHL designate fixing holes, into which areinserted fixing members such as nylon rivets for fixing the invertercircuit substrate IPCB; letters CW designate notches for the connectorsto be connected with the outside; and letters FKP designate fixingprojections (as shown at the individual sides of FIG. 34 and in FIG.36), in which are fitted fixing hooks FK of the shield casing SHD.

BACK LIGHTS BL

FIG. 37 presents the upper side, rear side, righthand side and lefthandside showing the state in which the back light support BLS, the backLights BL and the inverter circuit substrate IPCB are mounted in thelower casing LCA, and FIG. 39 is a section taken along line 39--39 ofFIG. 37.

The back lights BL are of the below lights type, in which it is arrangedjust below the liquid crystal display LCD. The back lights BL areconstructed of four cold-cathode fluorescent lamps and is supported bythe back light support BLS. The back lights BL are held in the lowercasing LCA or the back light mounting casing by fixing the back lightsupport BLS in the lower casing LCA through the through holes SHL of theback light support BLS and the screw holes LVH of the lower casing LCAby means of the not-shown screws.

Letters ECL designate the sealed side of the cold-cathode tube (at whicha fluorescent substance is applied to the inner surface of the tube, orthe tube is evacuated or filled with the gas). As shown in FIG. 37, thefour juxtaposed back lights BL are arranged such that their sealed sidesECL are horizontally staggered (or vertically staggered as in FIG. 37).As a result, the transverse gradations of the color temperatures (whichare higher at the sealed sides) on the display frame, which are causedas a result of applying the fluorescent substance to the fluorescentlamps, can be made less outstanding to improve the display quality.

INVERTER CIRCUIT SUBSTRATE IPCB

The inverter circuit IPCB is a circuit substrate for lighting the fourback lights BL is placed in the lower casing LCA, as shown in FIG. 37,and fixed through the fixing holes IHL (as shown in FIGS. 34 to 36) ofthe lower casing LCA by means of the not-shown fixing members such asnylon rivets. On the inverter circuit IPCB, there are mounted twotransformers TF1 and TF2 and electronic parts such as capacitors, coilsor resistors. Incidentally, the inverter circuit substrate IPCB actingas a heat source is arranged in the upper portion (as shown at thelefthand side of the upper side of FIG. 37) of the device so that it hasan excellent heat dissipation. Moreover, the inverter circuit substrateIPCB is arranged in the upper side of the device, whereas the L-shapeddrive circuit substrate PCB2 is arranged in the lower and lefthand side(i.e., in the L-shaped region of the righthand and lower edges of themiddle frame MFR, as viewed in FIG. 27) of the device. Thus, theinverter circuit substrate IPCB and the drive circuit substrate PCB2acting as the heat sources are so arranged as not to overlap each otherin view of the heat dissipation and the small thickness of the totalthickness of the module.

BACK LIGHTS BL, BACK LIGHT SUPPORT BLS AND INVERTER CIRCUIT SUBSTRATEIPCB

After the four back lights BL each having leads LD (as shown in FIG. 37)at its two ends have been fitted in the back light support BLS, (beforethe back light support BLS and the inverter circuit substrate IPCB aremounted and fixed in the lower casing LCA), the leads LD of each backlight BL are soldered to the inverter circuit substrate IPCB. As aresult, the back lights BL, the back light support BLS and the invertercircuit substrate IPCB constitute together one unit (as shown in FIGS.23 and 37). In this state, the lighting tests of the back lights BL canbe accomplished. In the prior art, the leads of the back lights aresoldered to the inverter circuit substrate after the back lights and theinverter circuit substrate have been individually fixed in the backlight mounting casing. The space for the soldering operation is solimited that its working efficiency is insufficient. In the presentmodule, the leads LD of the back lights BL can be soldered to theinverter circuit substrate IPCB with the back lights BL being supportedby the back light support BLS, before the back lights BL and theinverter circuit substrate IPCB are fixed in the lower casing LCA. Thus,the working efficiency is excellent. Moreover, defective parts, if any,can be easily replaced by new ones. After the lighting tests have beenended, the inverter circuit substrate IPCB is fitted through the fixingholes IHL of the lower casing LCA by using the fixing members such asnylon rivets, as shown in FIG. 37, and the back light support BLS isfixed in the lower casing LCA through the four through holes SHL andscrew holes LVH (as shown in FIGS. 36 and 34) by means of the not-shownscrews.

In the prior art, moreover, the construction is made to use sixcold-cathode tubes; and two inverter circuit substrates to light threecold-cathode tubes for each inverter circuit substrate (having twotransformers), and the two inverter circuit substrates are arranged atboth the upper and lower sides (or at the righthand and lefthand sidesof the upper side of the lower casing LCA, as viewed in FIG. 37) of theback lights in the back light casing. As a result, the total size of theback light portion is enlarged. Since the two inverter circuitsubstrates acting as heat sources are arranged vertically at the twosides, a problem arises in the heat dissipation. In the present device,however, the use of a single inverter circuit substrate IPCB can reducethe total size of the back light portion and can provide an excellentheat dissipation. In the present device, moreover, the inverter circuitsubstrate IPCB is arranged in the upper side (as shown at the lefthandside of the upper side of FIG. 37) of the device, an excellent heatdissipation can be achieved.

As has been described hereinbefore, according to the embodiments of thepresent invention, the fixing pawls and fixing hooks of the shieldcasing can be easily removed, and the shield casing, the middle framefor holding the liquid crystal display and the lower casing for mountingthe back lights can be easily disassembled and assembled so that therepair and the replacement of the back lights can De easilyaccomplished.

What is claimed is:
 1. A liquid crystal display device comprising:alower casing for packaging a lighting means; a middle frame mounted onsaid lower casing and having an opening exposing said lighting means; aliquid crystal display panel having a driving circuit and held by saidmiddle frame; a shield casing made of a metal plate, having fixing pawlsand covering said liquid crystal display panel except for a displayportion of said liquid crystal display panel; and an optical diffusionboard diffusing light of said lighting means; wherein said fixing pawlsare bent in recesses which are formed in said middle frame for fixingsaid shield casing and said middle frame, wherein said middle framemounts therein said liquid crystal display panel and said opticaldiffusion board in superposition, and wherein said liquid crystaldisplay panel and said optical diffusion board have a gap between themwhich is sealed up by a spacing means.
 2. A liquid crystal displaydevice according to claim 1,wherein said shield casing has a fixinghooks separate from said fixing pawls, and said fixing hooks are fittedon projections which are so formed on said lower casing as to correspondto said fixing hooks.
 3. A liquid crystal display device comprising:aliquid crystal display panel having a driving circuit disposed aroundand connected with said liquid crystal display panel; a shield casingmade of a metal plate, having fixing pawls and covering said liquidcrystal display panel and said driving circuit except for a displayportion of said liquid crystal display panel; a middle frame holdingsaid liquid crystal display panel and said driving circuit, and havingan opening exposing said display portion of said liquid crystal displaypanel; a lower casing attached to said middle frame, packaging alighting means lighting said display portion of said liquid crystaldisplay panel through said opening of said middle frame; wherein saidfixing pawls are bent in the recesses which are formed in said middleframe for fixing said shield casing and said middle frame, and saiddriving circuit has a ground pad on at least one of a plurality ofdivisions of said driving circuit, wherein said shield casing hasprojections for electrically connecting to said ground pad.
 4. A liquidcrystal display device according to claim 3,wherein said shield casinghas fixing hooks separate from said fixing pawls, and said fixing hooksare fitted on projections which are so formed on said lower casing as tocorrespond to said fixing hooks.
 5. A liquid crystal display devicecomprising:a lower casing for packaging a lighting means; a middle framemounted on said lower casing and having an opening exposing saidlighting means; a liquid crystal display panel having a driving circuitand held by said middle frame; a shield casing made of a metal plate,having fixing pawls and fixing hooks, and covering said liquid crystaldisplay panel except for a display portion of said liquid crystaldisplay panel; wherein said fixing pawls are bent in a recesses whichare formed in said middle frame for fixing said shield casing and saidmiddle frame, said fixing hooks are fitted on projections which are soformed on said lower casing as to correspond to said fixing hooks,wherein said lower casing has a reflecting means reflecting the light ofsaid lighting means toward said liquid crystal display panel, and saidreflecting means and said lower casing are made of an integral member.6. A liquid crystal display device according to claim 5,wherein saidlighting means comprises a plurality of juxtaposed fluorescent lampshaving their sealed sides arranged alternately at the righthand andlefthand sides.
 7. A liquid crystal display device according to claim5,wherein said lighting means comprises a light support for supporting aplurality of juxtaposed fluorescent lamps of said lighting meansseparate from said lower casing, and said light support being mounted onsaid lower casing.